The applicants hereby claim priority to Japanese patent application No. 2002-069893, filed Mar. 14, 2002, which is incorporated by reference.
1. Field of the Invention
The present invention relates to a method of exposing the pattern of an exposure mask (referred to as xe2x80x9cmaskxe2x80x9d hereinafter) to the light, thereby imaging the mask pattern on a photosensitive material, and also relates to an aligner for executing the method. Especially, the invention relates to a preferable exposure method and aligner as an exposure technique applicable for instance to the photolithographic process in the manufacture of a semiconductor integrated circuit (SIC), a liquid crystal display (LCD), a flexible print circuit board and so on; and also as an exposure technique applicable for instance to a scanner for use in a printing plate maker, an electronic copy machine and so forth.
2. Prior Art
Among various kinds of aligners as used in the photolithographic process, one of the processes for manufacturing SIC, LCD, etc, there is an aligner called a projection aligner. This aligner exposes the mask pattern to the light to image it on the photosensitive material with the help of an imaging optical system. In case of the aligner of this kind, some include an imaging optical system arranged between a holder for holding the mask and a stage for supporting the photosensitive material.
In this projection aligner, if an imaging device used as the imaging optical system has a large dimension, the holder and the stage cannot help being arranged apart from each other at a large distance. In order to obviate inconvenience like this, there might be considered various things, for instance a mechanism for holding the holder and the stage in parallel, a mechanism for adjusting the relative position between the holder and the stage, and/or a mechanism for moving the holder and the stage and so on. It should not be forgotten, however, that newly designing and manufacturing such mechanisms with new dimension and accuracy never fails to invite considerable cost increase.
Furthermore, in the projection aligner, the holder is arranged on the upper side within the space of the optical system while the stage is arranged on the lower side within the same. Therefore, the projection aligner has to be designed always-taking account of the positional relation among the optical system, the holder, and the stage. This is another inconvenience to be removed.
In order to eliminate such inconvenience as described above, there has been proposed an projection aligner wherein the mask and the photosensitive material are supported by an identical stage such that the their respective surfaces on which the light is incident are on an identical plane, and the light from a light source is first incident on the mask, and then, the light passing through the mask forms an image on the photosensitive material by using the imaging optical system (U.S. Pat. No. 5,652,645 Specification).
Consequently, in case of the projection aligner as disclosed by the above USP, there is no need for various mechanisms to be prepared. For instance, it would be no longer necessary to prepare a mechanism for maintaining the parallelism which is required when vertically arranging the mask and the photosensitive material such that they sandwich the imaging optical system between them, the mechanism for adjusting the positional relation among three of them, and the mechanism for moving three of them. Even though they are needed, their structure would be much more simplified. This would be an advantageous point of the invention disclosed by the above USP. Also, it would be another merit of the invention of this USP that the space needed in the vertical direction is reduced.
In spite of advantageous points as described above, it seems that the projection aligner disclosed by the above USP still include the problems to be solved. For instance, in case of imaging the mask pattern on the photosensitive material film formed on a glass substrate for use in the LCD panel, the stage is required to have a dimension corresponding to the dimension of the mask and photosensitive material film as used, thus the necessary space being increased. Furthermore, it is also difficult and inconvenient to move the stage having a large dimension at a high speed due to its weight and inertia.
Still further, if the imaging optical system having a large dimension is used in order to realize the high precision exposure, for instance to realize a deeper depth of focus, the mask and the photosensitive material have to be arranged on the stage apart from each other at a large distance. In order to avoid this, if the imaging optical system is installed inside the projection aligner such that the light vertically runs inside the imaging optical system, there are caused such a problem that increases the space needed in the vertical direction as well as the optical path length from the mask to the photosensitive material.
Accordingly, an object of the invention is to make the space necessary for supporting the mask and the photosensitive material as small as possible.
According to the invention, there is provided an exposure method of exposing an exposure mask pattern on a photosensitive material. This method includes the steps of letting at least a part of the light emitted from a light source be incident on the mask supported by a supporting device; and forming an image of the mask pattern on the photosensitive material by guiding the reflecting light from the mask such that the photosensitive material supported by the supporting device receives the reflecting light coming from an incident direction which is different from the incidence direction of the light incident on the mask.
According to the invention, there is provided an aligner for exposing an exposure mask pattern on a photosensitive material. This aligner includes the first supporting device for supporting said mask such that said mask receives at least a part of the light from said light source; the second supporting device for supporting said photosensitive material such that said photosensitive material receives the reflecting light from said mask from the direction which is different from said incident light direction toward said mask; a half mirror arranged on the way of the light path between said light source and said mask, said half mirror allowing at least a part of the light from said light source to pass through itself and changing the proceeding direction of the reflecting light from said mask; and an imaging optical system for focusing the reflecting light from said half mirror into an image on said photosensitive material.
According to the invention, the reflecting light from the mask is guided to be incident on the photosensitive material from a certain light incidence direction, which is different from the incidence direction of the light incident on the mask. In other words, the incidence direction of the light incident on the mask is different from that of the above reflecting light incident on the photosensitive material.
Furthermore, according to the invention, neither the mask nor the photosensitive material is supported by an identical stage such that their respective light incidence faces come to be on the approximately same plane. Accordingly, it becomes free to properly select respective incidence directions of the reflecting light incident on the photosensitive material and the light incident on the mask such that they become different from each other. This would bring a considerable merit. For instance, if the incidence direction of the light incident on the mask is made opposite to that of the reflecting light incident on the photosensitive material, it will be possible to reduce a space for supporting the mask and the photosensitive material to be much smaller.
An exposure method according to the invention may further includes a moving step of two-dimensionally and relatively moving the light incident on the mask and the light incident on the photosensitive material to the supporting device. With this step, it becomes possible to two-dimensionally and relatively moving the exposure light to the mask and the photosensitive material, and to use even a region having a small area as an irradiation region for use in the light exposure (irradiation), thus making it possible to reduce the dimension of the light source device and the imaging optical system.
The above imaging step may include a direction change step of changing the proceeding direction of the reflecting light from the mask through a half mirror arranged on the way of a light path between the light source and the mask; and a step of further changing the proceeding direction of the light of which the proceeding direction has been changed through a plurality of reflecting mirrors and a least one imaging lens, and focusing the direction-changed light into an image on the photosensitive material through at least one imaging lens. With this, it becomes possible to let at least a part of the light from the exposure light source be incident on the mask as well as to change the proceeding direction of the reflecting light from the mask. Still further, it also becomes possible to easily invert the incidence direction of the light incident on the mask as well as the incidence direction of the reflecting light incident on the photosensitive material, thus the space necessary for supporting the mask and the photosensitive material becoming smaller.
The above imaging step may further include a step of changing the proceeding direction of at least a part of the light incident on a light incidence face by using a prism arranged on the way of the light path between the half mirror and the photosensitive material, the prism having a light incidence face on which the light is incident and an light exit face from which the incident light comes out. With this, it becomes possible to use an optical system having a small dimension, thus the size of the entire aligner becoming smaller.
The above light incidence step may further include a steps of letting at least a part of the light from the light source be incident on the second photosensitive material, which is supported by the supporting device so as to be located on the opposite side of the mask side. With this, it becomes possible to expose two photosensitive materials to the exposure light at a time.
The above imaging optical system may further includes the half mirror, a plurality of reflecting mirrors arranged on the way of the light path between the half mirror and the photosensitive material, and at least one imaging lens. With this, it also becomes possible to easily invert the incidence direction of the light incident on the mask as well as the incidence direction of the reflecting light incident on the photosensitive material, thus the space necessary for supporting the mask and the photosensitive material becoming smaller.
The above imaging optical system may further include a prism having at least two faces on the one of which the light is incident and from the other of which the incident light comes out. The prism is arranged on the way of the light path between the half mirror and the photosensitive material and changes the proceeding direction of at least a part of the light incident on the light incidence face. With this, it becomes possible to use an optical system having a small dimension, thus the size of the entire aligner becoming smaller.
The above first supporting portion may support the second photosensitive material to locate it on the side opposite to the light incidence side of the mask side. With this, it becomes possible to expose two photosensitive materials together to the exposure light at a time.
The invention will now be described in detail by way of several examples with reference to the accompanying drawings, wherein constituents of the invention having like function and structure will be denoted with like reference numerals and characters in order to avoid the redundant repetitive description.